Baby swallows food. Around 6 months of age, one can try giving the baby some baby cereal (prepared with water or formula). If the baby is able to move the cereal around in his mouth, and swallow most of it, they he is ready for solid baby foods. If the baby seems to keep sticking his tongue forward and push the cereal out, then he should keep practicing off and on for a few more weeks.
Look at them. Babies should begin solid foods sometime between 4-6 months. Observe your baby when you sit down and eat. Are they excited, interested in your food? If so, and they are in the correct age range its a good idea to try whole grain cereal as their introduction to solid food.